﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Bai25_C_Sharp
{
    abstract class absClass
    {
        public abstract int Add(int x, int y);
        public abstract int Mul(int x, int y);
    }
    abstract class absClass2 : absClass
    {
        public override int Add(int x, int y)
        {
            return x + y;
        }
    }
    class absDerived : absClass2
    {
        public override int Mul(int x, int y)
        {
            return x * y;
        }
    } 
}
